Centrifuge with sieve and method for operating said centrifuge

ABSTRACT

The present invention relates to a centrifuge that includes an inlet tube, a distributor, a centrifugal drum, a centrifugal chamber, a sieve and a solids collecting space. The present invention also relates to a method for cleaning the centrifuge including the step sieve opening the solids collecting space so that liquid from a liquid discharge space return flows through the sieve back into the solids discharge space, detaching one or more of solids and contaminants from the sieve and, discharging one or more of the solids and contaminants from the solids discharge space.

[0001] The invention relates to a centrifuge, particularly a separator, having an inlet tube and a distributor for introducing a material to be centrifuged into a centrifugal chamber bounded by a centrifugal drum, in which centrifugal chamber a sieve is arranged which essentially is arranged coaxially with respect to the inlet tube and/or distributor, the distributor being designed such that it guides the material to be centrifuged into an area of the centrifugal chamber which is arranged radially outside the outer circumference of the sieve—solids collecting space—so that, during the centrifugal separating, a liquid component of the introduced material to be centrifuged flows radially from the outside toward the inside through the sieve. The invention also relates to a method of operating the centrifuge.

[0002] A centrifuge of the above-mentioned type and a method of its operation are known from German Patent Document DE 25 29 614 C2. This document describes a device for the continuous rotation pressure filtration of liquid media. Filtrations in the sense of this document are sieve as well as membrane filtrations as well as micro- or ultrafiltrations. By means of a hydrostatic pressure difference, a concentrate flow component is generated parallel to the surface of the filter, for the purpose of which a hydrodynamic delivery pressure in the ring gap between the centrifugal drum and the coaxial drum-shaped filter element is generated in that the drum and the filter element are simultaneously acted upon by mutually different rotary frequencies. Allegedly, without the independent relative rotatability, an extremely surface-laminar cross-current component would be formed between the filters which has such a low efficiency that, already shortly after the start of the filtration, the fractionation process would cease as a result of polarization effects and pore sealing.

[0003] The separate rotatability of the sieve drum causes high constructive expenditures and thus considerably increases the costs of the centrifuge. For this reason, among others, it was found according to the invention that the described solution has not been successful in practice.

[0004] It is also noted that, despite the relative rotatability of the sieve drum with respect to the centrifugal drum, a rerinsing of the membrane by means of a rinsing liquid is often required. However, such a rerinsing requires expenditures and interrupts the centrifuging operation for a considerable period of time.

[0005] It is an object of the invention to further develop the initially described centrifuge such that, by means of simplified constructive and/or process-related expenditures, the problem of the clogging of the sieve by solid particles or the problem of an uncomplicated cleaning of the centrifuge is solved.

[0006] This task is achieved according to the invention, with respect to the centrifuge, by means of the object of claim 1 and, with respect to the method, by means of the objects of claims 16 and/or 17.

[0007] Advantageous further developments of the invention are contained in the subclaims.

[0008] Since the solids collecting space can be discontinuously closed, a return flow of the liquid component through the sieve takes place when the solids collecting space is opened up.

[0009] For discharging the solids, the solids collecting space is opened up—particularly by opening a piston side valve—, so that solids and/or contaminants attached to and/or deposited on the sieve or the sieve drum (and, under certain circumstances, also cloggings or cakings) are discharged through the opening(s) (opened up by the piston slide valve).

[0010] In a simple fashion, this creates a cleaning effect of the sieve, because, when the piston slide valve is opened, liquid flows from the liquid discharge space through the sieve back into the solids collecting space, whereby solids clogging the sieve are now detached from the sieve and are discharged through the opening(s) opened up by the piston slide valve.

[0011] The invention therefore utilizes the unexpected effect that, when the piston slide valves, which are known per se, are opened for discharging the solids, the sieve is cleaned in a simple manner which virtually does not interrupt the centrifuging operation. A special advantage of this cleaning is the fact that the return flow can take place without the additional use of a rinsing liquid and that, only after a relatively long operation, a rerinsing by means of such a rinsing liquid will be required. It should also be stressed that, because of modern control techniques, it is possible to control the emptying mechanism very precisely and thereby also control the cleaning effects in a desired manner.

[0012] As a result of the cleaning effect, a long service life of the membrane insert is therefore achieved without the requirement of a production stop because of clogging. As a result of the rapidity of the emptying mechanism and the realizable controlling of the discharge volume, the intensity of the cleaning effect can be controlled as a function of the product.

[0013] The discharge of the concentrate by way of a separating plate or small tube, by way of ducts and nozzles outside the membrane insert is also conceivable. As a function of the product, this may lead to a lengthening of the rerinsing intervals (emptying intervals). An automating of the point of time of the emptying by monitoring the component discharged there is also conceivable.

[0014] The draining of a partial flow of the concentrate by way of nozzles at the piston slide valve is also conceivable. For such a discharge by means of nozzles at the piston slide valve, reference is made to German Patent Document DE 22 14 487.

[0015] Instead of a piston slide valve, an analogously functioning, discontinuously operating opening mechanism can be used which is arranged radially outside the sieve drum.

[0016] The relative rotatability between the sieve drum and the drum shell therefore no longer has to be realized although, in principle, this measure can naturally also be combined arbitrarily with the idea of the present invention. In principle, the invention can also be combined with the idea, also known per se, of a device for the continuous discharge of a solid component arranged in the solids collecting space, as long as the above-described flow-back effect is utilized for the cleaning.

[0017] It is particularly advantageous to assign to and/or connect behind particularly the sieve drum a stack of plates so that, after the clarification of the product in the sieve drum, a separation of different liquid components from one another can take place in the stack of plates.

[0018] In a particularly simple manner, the invention combines the technology of modern piston slide valve separators known per se with the idea of a membrane sieve and thereby provides a type of “membrane separator” with the option of a component separation on the output side in a plate stack which optionally in a surprising manner easily solves the problem of the clogging of the sieves of the separators.

[0019] The solids collecting space preferably has a double-cone shape, and the sieve is designed as a membrane sieve, particularly as a ceramic membrane sieve.

[0020] In the following, embodiments are described in detail with respect to the drawing.

[0021]FIG. 1 is a sectional view of a centrifuge, the left part of the figure showing the flow conditions during the separation centrifuging, and the right part of the figure showing the flow conditions during the cleaning;

[0022]FIG. 2 is a sectional view of a section of another centrifuge; and

[0023]FIG. 3 is a sectional view of another centrifuge, in the left part of the centrifuge, the option of a combination of a sieve and a plate stack being shown as an example.

[0024]FIG. 1 shows a separator 1 having an inlet tube 3 which leads into a distributor 5 which is used for introducing a material to be centrifuged into a double-cone centrifugal chamber 9 bounded by a (one-part or multi-part) centrifugal drum 7, in which centrifugal chamber 9 a membrane sieve is arranged in a construction as a sieve drum 11 of a ceramic material.

[0025] The distributor 5 extends into the lower area of the centrifugal drum 7 and is connected in its lower area with the lower edge of the sieve drum 11, so that the material to be centrifuged in the lower area of the centrifugal drum 7 is guided radially to the outside into the area outside the outer circumference of the sieve drum 11 which forms a solids collecting space 13. From here, the liquid component P of the introduced material to be centrifuged, during the separation centrifuging, flows radially from the outside toward the interior through the membrane of the sieve drum 11. In the upper area, the sieve drum has a conical shape and, in the area of a ring groove 23 ending with the sealing device 25, rests in sections against the interior wall of the centrifugal drum 7.

[0026] The solids collecting space 13 can be discontinuously opened and closed by means of piston slide valves 15. During the opening of the piston slide valve 15, the solids are guided toward the outside from the solids collecting space. In this case, a return flow is generated from the liquid discharge space 19 within the sieve drum 22 constructed as a sieve shell through the sieve shell, which return flow detaches solids deposited on the sieve shell and guides them to the outside also through the piston slide valve openings 21.

[0027] From the liquid discharge space, the liquid component P is discharged through ducts 17 and/or by means of grippers.

[0028]FIG. 2 shows a duct 27 in the wall of the centrifugal drum 7 for discharging the solid component.

[0029]FIG. 3 shows another embodiment of the invention in which a plate stack 29 was inserted into the sieve drum 11. Only as an example, the plate stack 29, which extends all around, was outlined only in the left part of FIG. 3. The plate stack 29 extends in a constructively simple manner from the upper conical interior wall of the centrifugal drum 7 downward to the wall of the sieve drum 11 and may be fastened to the sieve drum 11. A holding device 43 at the outer circumference of the plate stack 29, which is fastened to the sieve shell 11 or to the centrifugal drum 7, carries the plates of the plate stack 29 in a constructively simple manner.

[0030] In the plate stack, rising ducts 31 are constructed to which the product is fed by way of at least one or several feeding ducts 33 at the lower edge of the plate stack 29 (constructed, for example, between the plate stack 29 and the sieve drum 11).

[0031] Discharge ducts 35, 37 at the outer circumference and at the inner circumference of the plate stack permit the discharging of various liquid components which are separated from one another when flowing through the plate stack. The two discharge ducts 35 and 37 lead into additional discharge ducts 39, 41 in the wall of the centrifugal drum 7.

[0032] This variant of the invention has the following advantage. First, the sieving of the product to be clarified takes place in the manner of FIG. 1. After passing through the sieve drum 11, the clarified product enters the plate stack 29 through the feeding duct 33. Two liquid components of different densities are separated from one another there and are then discharged by way of the discharge ducts 35, 37 at the inner and outer circumference of the plate stack 29 and the additional adjoining discharge ducts 39, 41.

[0033] Reference Numbers

[0034] Separator 1

[0035] Inlet tube 3

[0036] Distributor 5

[0037] Centrifugal drum 7

[0038] Centrifugal chamber 9

[0039] Sieve drum 11

[0040] Solids collecting space 13

[0041] Piston slide valve 15

[0042] Ducts 17

[0043] Liquid discharge space 19

[0044] Piston slide valve openings 21

[0045] Ring groove 23

[0046] Sealing device 25

[0047] Duct 27

[0048] Plate stack 29

[0049] Rising ducts 31

[0050] Feeding ducts 33

[0051] Discharge ducts 35, 37

[0052] Discharge ducts 39, 41

[0053] Holding device 43 

1. Centrifuge, particularly a separator, a) having an inlet tube (3) and a distributor (5) for introducing a material to be centrifuged into a centrifugal chamber (9) bounded by a centrifugal drum (7), b) in which centrifugal chamber (9) a sieve is arranged which essentially is arranged coaxially with respect to the inlet tube (3) and/or the distributor, c) the distributor being designed such that it guides the material to be centrifuged into an area of the centrifugal chamber (9) which is arranged radially outside the outer circumference of the sieve—solids collecting space (13)—so that, during the centrifugal separating, a liquid component of the introduced material to be centrifuged flows radially from the outside toward the inside through the sieve (11), d) the solids collecting space being discontinuously closable so that, when the solids collecting space (13) is opened, a return flow of the liquid component takes place through the sieve.
 2. Centrifuge according to claim 1, characterized in that the solids collecting space (13) is closed by a piston slide valve (15).
 3. Centrifuge according to claim 1, characterized in that the solids collecting space (13) has a double cone shape.
 4. Centrifuge according to claim 1 or 2, characterized in that the sieve is a membrane sieve.
 5. Centrifuge according to claim 3, characterized in that the sieve is a ceramic membrane sieve.
 6. Centrifuge according to one of the preceding claims, characterized in that the sieve is constructed as a sieve drum (11).
 7. Centrifuge according to one of the preceding claims, characterized in that the distributor (5) extends into the lower area of the centrifugal drum (7) and/or is connected with the lower edge of the centrifugal drum (11).
 8. Centrifuge according to one of the preceding claims, characterized in that a device for the continuous discharge of the solid component is arranged in the solids collecting space (13).
 9. Centrifuge according to claim 5, characterized in that the device for the continuous discharge of the solid component is a separating plate, a tube, a duct (27) or a nozzle.
 10. Centrifuge, particularly a separator, preferably according to one of the preceding claims, or according to the characteristics a) to c) of claim 1, characterized in that a plate stack (29) is assigned to the sieve and/or connected to its output side.
 11. Centrifuge according to claim 10, characterized in that the plate stack (29) is inserted into the sieve drum (11).
 12. Centrifuge according to claim 11, characterized in that the plate stack (29) extends from the interior wall of the centrifugal drum (7) to the wall of the sieve drum (11).
 13. Centrifuge according to one of claims 10 to 12, characterized in that rising ducts (31) are constructed in the plate stack, to which the product is fed by way of feeding ducts (33).
 14. Centrifuge according to one of claims 10 to 13, characterized in that discharge ducts (35, 37) are constructed on the outer circumference and the inner circumference of the plate stack (29).
 15. Centrifuge according to one of claims 10 to 14, characterized in that a holding device (43) at the outer circumference of the plate stack (29), which is fastened to the sieve shell (11) or to the centrifugal drum (7), carries the plates of the plate stack (29).
 16. Method of operating a centrifuge according to one or several of the preceding claims, characterized in that, for cleaning the centrifuge, the solids collecting space is opened, so that liquid from the liquid discharge space flows through the sieve back into the solids collecting space, whereby solids and/or contaminants adhering to and/or deposited on the sieve are detached from the sieve and are discharged from the solids collecting space.
 17. Method of operating a centrifuge according to one or several of the preceding claims, characterized in that, for cleaning the centrifuge, the piston slide valve closing the solids collecting space is opened, whereby the solids and/or contaminants adhering to and/or deposited on the sieve are detached from the sieve and are discharged through an opening or openings opened up by the piston slide valve. 